1. Field of the Invention
The present invention relates to a switching station, a subscriber location information registration method, a subscriber service information acquisition method, a subscriber service information registration method, and a subscriber service information transmission method.
2. Description of the Related Art
There are two methods for mobility control in mobile communication: an HLR (Home Location Register) method in which location information and service information of subscribers (users) are managed by an apparatus physically separated from a switching station; and a VLR (Visited Location Register) method in which subscriber location information and service information are managed by a VLR in a switching station.
In the case of the VLR method, if the location of a user cannot be registered after the maximum number of accommodated users has been reached, neither of call origination and call termination by the user is allowed.
In connection processing of location registration function, call origination function and call termination function of the VLR method, when a mobile station moves into an area covered by a switching station, the mobile station recognizes change of location area and transmits a location registration signal to the switching station. The switching station acquires subscriber service information about the mobile station from the switching station in whose coverage area the mobile station has been located (from the HLR at the time of the first location registration). Also, information on the location of the mobile station used at the time of call termination is registered in the HLR. When the mobile station makes a call origination, the switching station performs call origination processing by using subscriber service information from the VLR. At the time of call termination, call termination processing is performed by using the (subscriber) location information from the HLR.
FIG. 1 is a diagram showing an example of a conventional mobile communication system and an example of processing when a location registration request is made. Referring to FIG. 1, switching stations 11 and 12 have VLR 21 and 22, respectively.
When a mobile station 50 moves from an (service) area 32 of the switching station 12 into an area 31 of the switching station 11 having the VLR 21 which has accepted the maximum number of subscribers, the switching station 11 receives a location registration (request) signal from the mobile station 50 (in S11 of FIG. 1) and acquires (in S12) subscriber service information about the mobile station 50 from the switching station 12 in whose coverage area the mobile station 50 has been located. However, no subscriber service information can be newly registered in the VLR 21 (in S13). Therefore location registration processing ends in failure (in S14) and updating (registration) of subscriber location information in an HLR 40 is not performed. If the subscriber makes call origination in such a situation, call origination processing is not normally performed since the switching station 11 has no service information about the subscriber on the VLR 21. Call termination processing also ends in failure since the subscriber location information in the HLR 40 has not been updated.
The number of subscribers (subscriber information items) possible to be registered in the VLR depends on hardware resources. Also, because the hardware resources are fixedly assigned, it is not possible to manage information on dynamically changing subscribers (users) with flexibility.